1.1 Technical Field
The present invention relates to a new process for obtaining .beta.-hydroxy carbonyl compounds and/or .alpha.,.beta.-unsaturated carbonyl compounds. More particularly its subject-matter is a process for aldolization and/or aldolization-crotonization of an aldehyde and/or of a ketone.
1.2 Description of Related Art
Industrial processes based on the reaction of aldol condensation of aldehydes and of ketones utilize a basic catalyst such as dilute solutions of potassium hydroxide and sodium hydroxide. The separation of these catalysts at the end of the reaction is not, however, easy and requires the addition of acidic solutions, especially sulfuric acid, to convert the catalysts into the corresponding salts. In addition, the removal of salts thus formed, which is necessary for the protection of the environment, is costly for industry.
To overcome the above-mentioned disadvantages the use of solid catalysts has been proposed. Thus, copper oxide supported on a .gamma.-alumina has been described in U.S. Pat. No. 4,739,122 for catalyzing the reaction of mixed aldol condensation between acetone and butanal.
U.S. Pat. No. 5,144,089 discloses a process for liquid-phase aldol condensation, especially the conversion of butanal to 2-ethyl-2-hexenal in the presence of a solid catalyst. The catalyst is a solid solution of magnesium oxide and aluminum oxide, derived from a hydrotalcite and has a specific surface area greater than 250 m.sup.2 /g.
Titanium dioxide has also been described as catalyst for the aldol condensation reaction in the process for obtaining .alpha.,.beta.-unsaturated aldehydes (U.S. Pat. No. 4,316,990).
Catalysis on an ion exchange resin has also been used but without great success, because the resin cannot withstand a temperature higher than 90.degree. C. In addition, once the resin is deactivated, it can no longer be regenerated.